Polishing tool and apparatus for polishing a workpiece

ABSTRACT

The present invention relates to a polishing tool 10 comprising a holder 11, a ball 12 received in the holder 11, and a polishing foil 13 covering all or part of the free surface 12a of the ball 12.

The present invention relates to a polishing tool according to the preamble of claim 1 and to an apparatus according to the preamble of claim 11.

A generic polishing tool is known from DE 10 2016 006 741 A1. The generic polishing tool has a curved head that carries a flexible or elastic polishing element to form a curved or domed polishing surface. Such a polishing tool is used in particular for zonal polishing of optical workpieces.

In zonal polishing, the polishing surface of the polishing tool is only partially placed against the workpiece to be polished in the region of a contact surface. This contact surface is considerably smaller compared to the surface of the workpiece to be polished, in particular compared to the radial extension of the workpiece.

Preferably, a different polishing tool is selected depending on the surface to be polished, in particular the (curvature) radius of the workpiece. Namely, in particular for zonal polishing, it is preferred that the (curvature) radius of the workpiece is larger than the (curvature) radius of the polishing surface of the polishing tool, preferably by at least a factor of two.

Zonal polishing allows in particular also polishing of aspherical and/or freely shaped surfaces of workpieces and is preferably used for precision optics, e.g. for mirrors or lenses, or for correcting manufacturing defects.

The domed head of the generic polishing tool is usually produced by turning. In order to achieve the desired precision in zonal polishing, it is necessary that the domed polishing surface of the polishing tool has a defined, exact dimension/shape or a geometry with very small geometric deviations.

Further, it is necessary that the polishing tool deforms deterministically and repeatably when pressed against the workpiece in order to achieve an optimum polishing result.

This requirement makes the manufacture of such a polishing tool, in particular the domed head, very complex and costly. Furthermore, the structure of the generic polishing tool requires that it be regularly dressed in use.

The object of the present invention is thus to improve a generic polishing tool or to further develop it in such a way that its manufacture is simplified, in particular while retaining the exact dimensioning and/or geometry of the domed head.

The solution of this problem consists in a polishing tool with the features of claim 1 as well as in an apparatus with such a polishing tool according to claim 11.

According to the invention, a holder is provided which is suitable for being connected—in particular in a form-fitting and/or force-fitting manner—to a tool spindle. The holder preferably has an in particular concave, especially preferably spherical, receptacle in which a preferably elastically or elastically deformable ball—in particular with defined dimensions and defined (Shore) hardness—is received. The free surface of the ball, and/or the surface of the ball facing away from the holder, is preferably provided directly with a polishing film/polishing foil.

The polishing tool according to the invention is very easy to manufacture. In particular, the dimensioning and/or geometry of the ball can be realized extremely precisely and reproducibly, so that in the end result a high-precision polishing tool is provided, in particular for the zonal polishing of optical workpieces.

Dressing, in particular correction of the geometric shape, of the polishing tool according to the invention during use is not necessary.

The size and properties of the polishing tool according to the invention can furthermore be easily adapted to the requirements of the workpiece to be polished. In particular, a ball with the (Shore) hardness required in the individual case can be selected and received/accommodated in the holder as often as desired, or a suitable polishing foil with the polishing properties desired in the individual case can be selected and attached to the free surface of the ball.

The holder can, for example, be made of a plastic, in particular (injection) molded. A suitable plastic is in particular rigid PVC (uPVC).

The ball is preferably elastic or elastically deformable and/or can, for example, be made of a rubber material that has a defined (Shore) hardness, for example in the range from SH 50 to SH 65.

The polishing foil is preferably kept in advance in the form of an unfolded sphere and/or cut to size in the form of an unfolded sphere and is attached, in particular adhered/glued, to the free surface of the ball stress-free and/or wrinkle-free.

The unfolded sphere can be cut out from a planar polishing foil and attached to the free surface of the ball.

A suitable material for the polishing foil is, for example, polyurethane LP-13 with a thickness of 0.5 mm.

As a result, a high-precision polishing tool with a long service life is obtained that is easy and inexpensive to manufacture, which polishing tool—in particular due to the high-precision attachment of the polishing foil to the ball—does not need to be dressed during manufacture and/or use.

The polishing tool according to the invention enables, in particular due to the deterministic uniform elastic properties, a uniform removal even over a longer period of time and/or after several polishing processes and thus an optimum polishing result.

The aforementioned aspects and features as well as the aspects and features of the present invention resulting from the claims and the following description can in principle be realized independently of each other, but also in any combination.

Further aspects, advantages, features, characteristics as well as advantageous further developments of the present invention result from the dependent claims and the following description of preferred embodiments based on the figures. It shows in schematic, not to scale views:

FIG. 1a a first exemplary embodiment of a polishing tool according to the invention in a perspective, exploded view;

FIG. 1b the polishing tool according to FIG. 1a in an assembled state;

FIG. 2 another example of an unfolded sphere for a polishing foil;

FIG. 3a a schematic section of the polishing tool according to the invention according to a further embodiment;

FIG. 3b a schematic section of the polishing tool according to FIG. 3a in the region of a receptacle for a ball;

FIG. 4a a schematic section of the polishing tool according to the invention according to a further embodiment;

FIG. 4b a schematic section of the polishing tool according to FIG. 4a in the edge region of the receptacle for the ball not shown;

FIG. 5a a schematic section of the polishing tool according to the invention according to a further embodiment;

FIG. 5b a schematic section of the polishing tool according to FIG. 5a in the edge region of the receptacle for the ball not shown;

FIG. 6a a schematic section of the polishing tool according to the invention according to a further embodiment; and

FIG. 6b a schematic section of the polishing tool according to FIG. 6a in the edge region of the receptacle for the ball not shown.

In the figures, some of which are not to scale and are merely schematic, the same reference signs are used for the same, similar or alike parts and components, wherein corresponding or comparable properties and advantages are achieved, even if a repeated description is omitted.

In the exemplary embodiment according to FIGS. 1a and 1b , the polishing tool 10 according to the invention is composed of a holder 11, a ball 12 and a polishing film/polishing foil 13 preferably in the form of an unfolded sphere.

However, the polishing tool 10 according to the invention may also have other components and/or parts.

The holder 11 is preferably designed to hold the ball 12 in a form-fitting, force-fitting and/or bonded manner, in particular immovably, and/or to connect the ball 12 to a tool spindle (not shown).

The polishing tool 10, in particular the holder 11, is preferably at least essentially cylindrical and/or designed as a (circular) cylinder.

Particularly preferably, the polishing tool 10 and/or the holder 11 are/is at least substantially rotationally symmetrical.

Preferably, the polishing tool 10 has a tool axis A1, in particular wherein the tool axis A1 forms a longitudinal, symmetrical, central and/or rotational axis of the preferably elongated and/or rotationally symmetrical polishing tool 10 and/or the preferably elongated and/or rotationally symmetrical holder 11.

The spatial assignments, arrangements and/or alignments, in particular the terms “radial” and/or “axial” used in the context of the present invention, preferably refer to the tool axis A1—unless otherwise indicated.

The holder 11 has an adapter region 11 a for connection to and/or reception in a tool spindle (not shown) and a recess or receptacle 11 b, in particular for the ball 12.

Preferably, the adapter region 11 a forms a first and/or workpiece-remote (axial) end and the receptacle 11 b forms a second and/or workpiece-near (axial) end of the holder 11.

In particular, the adapter region 11 a and the receptacle 11 b are located on opposite sides and/or ends of the holder 11.

Preferably, the adapter region 11 a is cylindrical and/or formed by a (circular) cylinder.

Preferably, the adapter region 11 a has a constant diameter—in particular along the tool axis A1—especially of at least essentially 25 mm.

Preferably, the length and/or axial extension of the adapter region 11 a is at least essentially 42 mm.

The adapter region 11 a can preferably be mounted/clamped in a tool chuck of a tool spindle.

The holder 11 is preferably formed in one piece. However, it is also possible for the holder 11 to be made up of multiple parts and/or to be assembled by a plurality of components.

In the exemplary embodiment, the holder 11 is (injection-)molded from a suitable plastic, e.g. rigid PVC (uPVC), in a manner known per se.

The receptacle 11 b is preferably designed to receive the ball 12. In particular, the receptacle 11 b is designed to hold the ball 12 in a form-fitting, force-fitting and/or bonded manner.

Preferably, the receptacle 11 b is concave, in particular spherical, especially preferably at least substantially hemispherical. In particular, the receptacle 11 b is designed as a spherical cap and/or spherical shell.

The recess or receptacle 11 b is dimensioned so that it can receive/accommodate a ball 12, preferably free of clearance/free of play, as will be explained in more detail below.

In the exemplary embodiment, the ball 12 is made of solid rubber to exact dimensions and preferably has a Shore hardness of SH 50 to SH 65.

The ball 12 can be glued/adhesively bonded in the recess 11 b, for example. However, solutions are also possible in which the ball 12 is additionally or alternatively held in the recess 11 b in a form-fitting and/or force-fitting manner, as will be explained in more detail below.

In the fully assembled state, as shown in FIG. 1b , a (first) part of the ball 12 is recessed/inserted into the holder 11 and/or a (second) part of the ball 12 protrudes from the holder 11.

Consequently, the ball 12 can be partitioned/subdivided into two parts or segments/caps, as indicated by a dashed line in FIG. 1 a.

In particular, the ball 12 has a first and/or free spherical cap and a second and/or concealed/covered and/or retained/held spherical cap, wherein the first and/or free spherical cap of the ball 12 projects out of the holder 11, in particular the receptacle 11 b, and the second and/or concealed/covered and/or retained/held spherical cap is recessed/inserted into and/or retained/held by the holder 11, in particular the receptacle 11 b.

Especially preferably, the ball 12 is at least substantially partitioned/subdivided into two hemispheres and/or the first and/or free spherical cap and the second and/or concealed spherical cap are each formed as a hemisphere. In this way, on the one hand, a good connection between the ball 12 and the holder 11 is made possible and, on the other hand, a sufficient surface area of the ball 12 is provided for polishing and/or attaching the polishing foil 13.

The ball 12, in particular the first spherical cap, preferably has a first and/or free surface and/or working surface 12 a, preferably wherein the free surface and/or working surface 12 a faces away from the holder 11, in particular the receptacle 11 b.

The ball 12, in particular the second spherical cap, preferably has a second and/or concealed/covered surface and/or holding surface 12 b, preferably wherein the holding surface 12 b faces the holder 11, in particular the receptacle 11 b.

In particular, (exclusively) the second spherical cap and/or the holding surface 12 b is connected to the holder 11, in particular the receptacle 11 b, in a form-fitting, force-fitting and/or bonded manner, in particular by gluing/adhesively bonding.

The polishing tool 10 preferably has the polishing foil 13 and/or a polishing surface 13 a, preferably wherein the polishing foil 13 and/or the polishing surface 13 a forms a (first) axial and/or free end of the polishing tool 10 and/or covers the ball 12 at least partially, in particular on a side facing away from the holder 11, and/or is in direct contact with a workpiece (not shown) during polishing of the workpiece.

The free surface 12 a of the ball 12 and/or the first spherical cap is preferably provided and/or coated/laminated with the polishing foil 13 directly or without an intermediate element.

Particularly preferably, the first spherical cap and/or the free surface or working surface 12 a of the ball 12 is completely or partially covered with the polishing foil 13.

Preferably, the polishing foil 13 is spaced from the edge of the holder 11 and/or the receptacle 11 b. It is thus preferred that the polishing foil 13 does not completely cover the first spherical cap and/or the free surface 12 a of the ball 12 and/or does not extend (exactly) to the edge of the holder 11 and/or the receptacle 11 b. In this way, folds/wrinkles are prevented from forming, for example, due to deformation of the ball 12 during polishing, which can impair the polishing result.

The polishing foil 13, in particular the polishing surface 13 a, is preferably (convexly) curved, in particular spherical. Particularly preferably, the curvature of the polishing foil 13, in particular the polishing surface 13 a, corresponds at least substantially to the curvature of the ball 12, in particular the free surface 12 a.

Consequently, the polishing foil 13 is preferably adapted to the ball 12 or the curvature of the ball 12.

It is preferred that the polishing foil 13 lies stress-free and/or wrinkle-free and/or flat on the ball 12, in particular the free surface or working surface 12 a.

By the term “stress-free” in the sense of the present invention, it is preferably to be understood that no (local) material deformations or stresses occur in the material of the polishing foil 13 and/or the ball 12 due to adaptation, in particular, of the polishing foil 13 to the curvature of the ball 12.

In particular, in order to adapt the polishing foil 13 to the ball 12, in particular the free surface 12 a of the ball 12, without wrinkles and/or stresses, the polishing foil 13 is preferably unwrapped/unfolded/developed, in particular as a spherical cap, and/or cut to size as an unwrapping/unfolding/development, in particular of a spherical cap.

The term “unwrapping/unfolding/development” in the sense of the present invention is preferably understood to mean the spreading of a surface, in particular a curved or three-dimensional surface, into a (two-dimensional) plane, in particular in such a way that the lengths of the surface are retained. For example, the lateral surface of a cylinder can be unwrapped/unfolded/developed (exactly) to a (plane) rectangle. A sphere can be unwrapped/unfolded/developed in an approximate or segmental manner.

In the embodiment example, the polishing foil 13 is provided as a corresponding unfolded sphere, in particular unfolded sphere segment, of the free surface 12 a of the ball 12.

The polishing foil 13 or the polishing surface 13 a is preferably segmented and/or formed by multiple, preferably at least four or six, in particular equally sized segments S.

In the embodiment shown in FIGS. 1a and 1b , the polishing foil 13 or the polishing surface 13 a is formed by four segments S. However, other solutions are also possible here, as will be explained in more detail below.

The segments S can abut one another laterally and/or in the circumferential direction of the ball 12 and/or be spaced apart from each other laterally and/or in the circumferential direction of the ball 12.

In particular, embodiments are possible in which the segments S are spaced apart in such a way that channels are formed between the segments S.

The channels of the polishing foil 13 and/or between the segments S preferably intersect on the front side of the polishing tool 10 and/or in the tool axis A1 and extend from the point of intersection to the edge of the holder 11 and/or the receptacle 11 b.

In particular, it is possible for the channels to widen from the point of intersection to the edge of the holder 11 and/or the receptacle 11 b.

Through the channels, a polishing agent (not shown) can distribute evenly over the polishing surface 13 a. Furthermore, abrasion of the workpiece and/or the polishing foil 13 can collect in the channels.

The polishing foil 13 preferably has a thickness of at least 0.1 mm, in particular at least 0.3 mm, particularly preferably at least 0.4 mm, and/or at most 3 mm, in particular at most 2 mm, particularly preferably at most 1 mm.

Especially preferably, the polishing foil 13 has a thickness of at least essentially 0.5 mm. A polishing foil 13 that is too thick does not adapt so well to the curvature of the ball 12, so that dressing of the polishing tool 10 may be necessary during manufacture. A polishing foil 13 that is too thin, on the other hand, can tear more quickly during polishing.

Preferably, the polishing foil 13 is made of an in particular porous and/or structured plastic film/plastic foil, for example of polyurethane, preferably wherein a filler material and/or polishing material is introduced into the polishing foil 13.

In the exemplary embodiment, the polishing foil 13 is cut from a 0.5 mm thick film/foil of polyurethane LP-13 with cerium oxide as filler material and/or polishing material.

The polishing foil 13 can be glued/adhesively bonded to the free surface 12 a of the ball 12 and/or the first spherical cap.

The exemplary embodiment of the polishing foil 13 according to FIG. 2 illustrates that the sphere unfoldings can be designed differently depending on the size and the requirements of the individual case. While the polishing foil 13 according to FIG. 1a has the shape of a “flower-shaped” sphere unfolding with four “petals” or segments S, the polishing foil 13 according to FIG. 2 has the shape of a “flower-shaped” sphere unfolding with six “petals” or segments S.

As already explained, it is preferred that the segments S are of equal size and/or dimension. Preferably, the segments S are each formed as isosceles triangles with (slightly) convexly curved legs.

However, the polishing foil and/or polishing layer 13 can also be applied to the ball 12 in other ways. For example, it is possible to form the polishing foil 13 by dipping the ball 12 in a bath of a liquid and/or by spraying the ball 12 with a liquid.

In the following, in particular the receiving and/or mounting/fastening of the ball 12 in the holder 11 and/or receptacle 11 b shall be explained in more detail with reference to FIGS. 3 to 6.

The ball 12 is preferably formed in one piece.

Preferably, the ball 12 is elastic, in particular more elastic and/or more compliant and/or softer than the holder 11.

Preferably, the ball 12 has an elastic modulus/Young's modulus of at least 0.5 N/mm² or 1 N/mm² and/or at most 100 N/mm², 50 N/mm² or 10 N/mm².

The elastic modulus/Young's modulus is preferably a material parameter for the relationship between stress or pressure and strain or compression during the deformation of a (test) piece made of the material.

A material with a low elastic modulus is consequently softer and/or more elastic and/or easier to compress than a material with a higher elastic modulus.

Preferably, the ball 12 is made of a rubber material, in particular a synthetic rubber, for example acrylonitrile butadiene rubber.

The term “rubber material” in the sense of the present invention is preferably understood to mean all materials which are designed to be rubber-elastic. Elastomers, such as rubber, in particular natural rubber and/or synthetic rubber, such as silicone rubber, are particularly preferred to be understood as rubber materials in the sense of the present invention.

The term “elastic” or “elasticity” in the sense of the present invention is preferably to be understood as the property of a material to change its shape elastically, i.e. not plastically, when a force is applied and to return to its original shape when the applied force is removed—without permanent deformation.

Preferably, the Shore hardness, in particular the Shore D hardness, of the ball 12 is at least SH 30 or SH 40 and/or at most SH 70 or SH 65.

Hardness is preferably a material property that can be used as a measure of the (mechanical) resistance of a material to mechanical penetration by another body.

Preferably, the Shore hardness, in particular the Shore D hardness, is determined according to DIN EN ISO 868:2003-10 and/or DIN ISO 7619-1:2012-02.

The ball 12 preferably has a diameter of at least 5 mm or 10 mm, in particular at least 20 mm or 30 mm, and/or at most 100 mm or 80 mm, in particular at most 50 mm or 40 mm.

As already explained at the outset, the intended use of the polishing tool 10 requires that the polishing tool 10, in particular the ball 12, has a very precise geometry, i.e. a geometry with low geometric deviations and/or tolerances.

Against this background, it is preferred that the ball 12 is ground and/or has a roundness accuracy of 0.01 mm or 0.02 mm, preferably with the roundness being determined in accordance with DIN EN ISO 1101:2014.

FIG. 3a shows the polishing tool 10 according to a further embodiment in a schematic section. FIG. 3b is an enlarged view of the polishing tool 10 according to FIG. 3a in the region of the receptacle 11 b.

As already explained, the ball 12 is at least partially, preferably up to half, recessed or inserted into the holder 11, in particular the receptacle 11 b, in particular in such a way that the first spherical cap projects out of the holder 11 or the receptacle 11 b.

The receptacle 11 b is preferably (concavely) curved, in particular spherical. Particularly preferably, the curvature of the receptacle 11 b corresponds to the curvature of the ball 12 and/or the receptacle 11 b or an (imaginary) ball delimited by the receptacle 11 b has an (inner) diameter which corresponds at least substantially to the (outer) diameter of the ball 12 or is slightly larger than the (outer) diameter of the ball 12, for example by at most or exactly 0.5 mm or 1 mm. However, other solutions are also possible here, in particular in which the (inner) diameter of the receptacle 11 b or of an (imaginary) ball delimited by the receptacle 11 b is smaller than the (outer) diameter of the ball 12, preferably by at least or exactly 0.5 mm, 0.4 mm, 0.3 mm or 0.2 mm.

Preferably, the (largest) (inner) diameter of the receptacle 11 b or of an (imaginary) ball delimited by the receptacle 11 b is at least 10 mm, 20 mm or 30 mm and/or at most 100 mm, 50 mm or 40 mm.

Preferably, the depth or axial extension of the receptacle 11 b corresponds at least substantially to the radius of the ball 12.

It is preferred that the ball 12, in particular the second spherical cap or the second or concealed/covered surface 12 b is adhesively bonded to the holder 11 or the receptacle 11 b, as indicated by an adhesive seam or adhesive layer 14 in FIGS. 3a and 3 b.

In particular to prevent air from being trapped between the ball 12 and the holder 11 and/or adhesive from being forced out of the holder 11 or receptacle 11 b when the ball 12 is inserted into the holder 11 or receptacle 11 b, the polishing tool 10, in particular the holder 11, has a channel 15, preferably wherein the channel 15 opens axially and/or centrally into the receptacle 11 b.

The channel 15 preferably connects the receptacle 11 b to the environment/surroundings.

The channel 15 preferably has a first or axial channel portion 15 a and a second or radial channel portion 15 b.

Preferably, the channel 15, in particular the first channel portion 15 a, extends axially through the holder 11 and/or from the adapter region 11 a to the receptacle 11 b.

Preferably, the second channel portion 15 b extends radially through the holder 11, in particular the adapter region 11 a, and/or transversely to the first channel portion 15 a. In the embodiment shown, the second channel portion 15 b extends completely through the holder 11 and/or from one side to the other. In this way, an imbalance is prevented from occurring.

Preferably, the channel 15 is formed by one or more bores in the holder 11.

Preferably, the channel 15 has a diameter of more than 1 mm and/or less than 5 mm, particularly preferably of at least substantially 3 mm.

When the ball 12 is inserted into the holder 11 or receptacle 11 b, air and/or adhesive can be pressed into the channel 15, in particular the first channel portion 15 a, in particular in such a way that the ball 12 is wetted and/or in contact with the adhesive layer 14 over its entire surface and/or without pressure.

By means of the first channel portion 15 a, pressure equalization is thus made possible when the ball 12 is inserted into the holder 11.

By means of the second channel portion 15 b, pressure equalization is made possible when mounting/clamping the polishing tool 10. In other words, when the polishing tool 10 is mounted/clamped into the tool spindle, it is prevented that air is pressed against the ball 12 and that the ball 12 possibly detaches from the holder 11.

By the second channel portion 15 b being preferably arranged in the adapter region 11 a, it is prevented that polishing agent and/or abrasion enters the second channel portion 15 b during the polishing process and possibly clogs it.

In addition or as an alternative to adhesive bonding, it is also possible to hold the ball 12 by means of the holder 11 or the receptacle 11 b in a force-fitting and/or friction-fitting and/or form-fitting manner.

Preferably, the receptacle 11 b has multiple, in particular two, regions or portions, particularly preferably wherein the regions differ from one another in geometry.

Preferably, the receptacle 11 b has a first or inner region 11 c and a second or outer region 11 d preferably immediately adjacent to the first region 11 c, preferably wherein the second region 11 d comprises or forms an axial end of the holder 11 or the receptacle 11 b.

The first region 11 c is preferably concave, in particular spherical. Particularly preferably, the curvature and/or diameter of the first region 11 c or of an (imaginary) ball delimited by the first region 11 c corresponds at least substantially to the curvature and/or diameter of the ball 12.

Consequently, the first region 11 c is preferably formed as a spherical cap or spherical shell, in particular wherein the radius of the spherical cap or spherical shell corresponds at least substantially to the radius of the ball 12.

The second region 11 d is preferably cylindrical. In particular, the second region 11 d is straight or not curved in the axial direction.

In particular, the diameter of the preferably cylindrical second region 11 d is smaller than the diameter of the preferably spherical first region 11 c and/or the ball 12, in particular by at least or exactly 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm or 0.5 mm.

Consequently, it is preferred that in the assembled state the second region 11 d or the holder 11 in the second region 11 d presses—in particular at least essentially radially—on the ball 12 and/or the ball 12 is held in the second region 11 d in a force-fitting manner.

In other words, an in particular annular (slight) press fit or centering fit for the ball 12 is preferably produced by means of the second region 11 d.

Preferably, a force fit between the ball 12 and the holder 11 is generated or a (frictional) force is exerted on the ball 12 exclusively in the second region 11 d or by the second region 11 d. Consequently, it is preferred that the ball 12 or the second spherical cap is received stress-free and/or pressure-free in the first region 11 c.

Preferably, the receptacle 11 b, in particular the second region 11 d, is designed in such a way that pressing onto the ball 12 is exclusively or at least predominantly radial or transverse to the tool axis A1. In this way, the ball 12 is held securely in the receptacle 11 b and/or the ball 12 is prevented from being pressed out of the holder 11.

Preferably, the depth or axial extension of the first region 11 c is smaller than the radius of the ball 12.

Preferably, the second region 11 d has a depth or an axial extension of at least 1 mm or 2 mm and/or at most 5 mm.

The second region 11 d preferably joins the first region 11 c continuously and/or steplessly. In particular, the first region 11 c merges continuously and/or steplessly into the second region 11 d. However, solutions are also possible in which the transition between the first region 11 c and the second region 11 d has a step or a kink.

FIGS. 3 to 6 illustrate that the holder 11 can be shaped differently and/or can have different sizes and/or diameters depending on the size of the ball 12 to be received and on the requirements of the individual case.

The polishing tools 10 shown in FIGS. 3 to 6 have basically a comparable construction and differ primarily in the dimensions of the receptacle 11 b.

As explained above, the polishing tool 10 has the adapter region 11 a for connection to a tool spindle (not shown).

Further, the polishing tool 10, in particular the holder 11, has a shaft 16 and a head 17, preferably wherein the shaft 16 connects the adapter region 11 a to the head 17.

Preferably, the polishing tool train 10, in particular the holder 11, has a stop 18 for defined mounting or holding of the polishing tool 10 to the associated tool spindle or its tool chuck.

The stop 18 serves in particular to establish a defined axial position of the polishing tool 10 relative to the tool spindle.

Preferably, the head 17 has or forms the receptacle 11 b. In particular, the receptacle 11 b is delimited or formed by the wall of the head 17.

In the embodiment shown in FIGS. 3a and 3b , the head 17 has the smallest (outer) diameter of the holder 11 and/or the (largest) (outer) diameter of the head 17 is smaller than the (outer) diameter of the adapter region 11 a.

Here, the shaft 16 is preferably formed as a cone or truncated cone and/or tapers in particular continuously in the direction of the head 17 or the receptacle 11 b.

The holders 11 shown in FIGS. 4 to 6 are preferably designed to receive a ball 12 that is larger compared to the embodiment according to FIGS. 3a and 3b , for example with a diameter of at least substantially 20 mm, 30 mm or 40 mm.

Preferably, the head 17 here is shaped like a mushroom-head and/or the (outer) diameter of the holder 11 increases from the shaft 16 to the head 17.

In particular, the (largest) (outer) diameter of the head 17 may be larger than the (largest) (outer) diameter of the shaft 16 and/or the adapter region 11 a, as illustrated in particular by the embodiment according to FIGS. 6a and 6 b.

In the embodiment shown in FIGS. 6a and 6b , the shaft 16 is at least substantially cylindrical and/or the shaft 16 has a constant (outer) diameter along the tool axis A1.

The proposed apparatus for polishing a workpiece preferably comprises a rotatably driven tool spindle and the proposed polishing tool 10, wherein the polishing tool 10 is interchangeably fastened or fastenable to the tool spindle.

Individual aspects and features of the present invention can be implemented independently from each other, but also in any combination.

LIST OF REFERENCE SIGNS

-   10 polishing tool -   11 holder -   11 a adapter region -   11 b recess/receptacle -   11 c first region -   11 d second region -   12 ball -   12 a free surface/working surface -   12 b concealed/covered surface/holding surface -   13 polishing foil -   13 a polishing surface -   14 adhesive layer -   15 channel -   15 a first channel portion -   15 b second channel portion -   16 shaft -   17 head -   18 stop -   A1 tool axis -   S segment of polishing foil 

1. A polishing tool, comprising: a holder, a ball received in the holder, a polishing foil covering all or part of the free surface of the ball.
 2. The polishing tool according to claim 1, further comprising a receptacle in which the ball is received.
 3. The polishing tool according to claim 1, wherein the holder is cast from a plastic.
 4. The polishing tool according to claim 1, wherein the ball consists of a rubber material.
 5. The polishing tool according to claim 1, wherein the ball has a Shore hardness of at least SH 30 or at most SH
 70. 6. The polishing tool according to claim 1, with the polishing foil at least one of having the shape of an unfolded sphere or being formed by a plurality of segments.
 7. The polishing tool according to claim 6, wherein the unfolded sphere or the segments is or are cut out of a flat foil.
 8. The polishing tool according to claim 1, wherein the polishing foil is attached to the free surface of the ball at least one of stress-free or wrinkle-free.
 9. The polishing tool according to claim 1, wherein the holder has a channel opening into the receptacle.
 10. The polishing tool according to claim 1, wherein the holder has a first, spherical, region and a second, cylindrical, region.
 11. An apparatus for polishing a workpiece, with a rotatably driven tool spindle and a polishing tool, wherein the polishing tool is exchangeably fastened or fastenable to the tool spindle, wherein the polishing tool comprises a holder, a ball received in the holder and a polishing foil covering all or part of the free surface of the ball.
 12. The polishing tool according to claim 2, wherein the ball is received in at least one of a force-fitting or bonding manner.
 13. The polishing tool according to claim 10, wherein the diameter of the second region is smaller than the diameter of the ball.
 14. The apparatus according to claim 11, further comprising a receptacle in which the ball is received.
 15. The apparatus according to claim 11, wherein the holder is cast from a plastic.
 16. The apparatus according to claim 11, wherein the ball consists of a rubber material.
 17. The apparatus according to claim 11, wherein the ball has a Shore hardness of at least SH 30 or at most SH
 70. 18. The apparatus according to claim 11, with the polishing foil at least one of having the shape of an unfolded sphere or being formed by a plurality of segments.
 19. The apparatus according to claim 11, wherein the polishing foil is attached to the free surface of the ball at least one of stress-free or wrinkle-free.
 20. The Apparatus according to claim 11, wherein the holder has a channel opening into the receptacle. 